Issue 49

M. J. Adinoyi et alii, Frattura ed Integrità Strutturale, 49 (2019) 487-506; DOI: 10.3221/IGF-ESIS.49.46

Focused on New Trends in Fatigue and Fracture

Analysis of Low-Cycle Fatigue Behavior of AW2099-T83 Al-Li Alloy

Muhammed J. Adinoyi, Necar Merah, Jafar Albinmousa Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia

mjadinoyi@gmail.com, http://orcid.org/0000-0001-2345-6789 nesar@kfupm.edu.sa, https://orcid.org/0000-0002-8158-8867 binmousa@kfupm.edu.sa, https://orcid.org/0000-0002-2395-5008

A BSTRACT . Microstructural characteristics, monotonic and strain-controlled cyclic axial behaviors of AW2099-T83 Aluminum-Lithium alloy were investigated. Grain sizes and structures are not uniform in the different orientations studied. High strength and low ductility characterize the tensile behavior of the alloy under static loading. Strain-controlled fatigue testing was conducted at strain amplitudes ranging from 0.3% to 0.7%. Over this range, macro plastic deformation was only observed at 0.7%. Cyclic stress evolution was found to be dependent on both the applied strain amplitude and the number of cycles. Limited strain hardening was observed at low number of cycles, followed by softening, due probably to damage initiation. With low plastic strain, analytical approach was adopted to profile the damaging mechanism for the different applied strain amplitude. Because of the absence of fatigue ductility parameters due to low plasticity, a three-parameter equation was used to correlate fatigue life. Fractured specimens were studied under SEM to characterize the fracture surface and determine the controlling fracture mechanisms. The fractography analysis revealed that fracture at low strain amplitudes was shear controlled while multiple secondary cracks were observed at high strain amplitude. Intergranular failure was found to be the dominant crack propagation mode. K EYWORDS . Aluminum-lithium; Microstructure; Fatigue behavior; Fatigue damage; Intergranular fracture.

Citation: Adinoyi, M. J., Merah, N., Albinmousa, J., Analysis of Low-Cycle Fatigue Behavior of AW2099-T83 Al-Li Alloy, Frattura ed Integrità Strutturale, 49 (2019) 487-506.

Received: 02.02.2019 Accepted: 14.04.2019 Published: 01.07.2019

Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

I NTRODUCTION

ightweight alloys such as aluminum (Al) alloys are crucial to the transportation sector, especially the aerospace industry. Aluminum alloys have a long history in the industry because of their low weight and considerable strength [1–4]. Therefore, the history of aircraft material cannot be told without aluminum occupying a prime position. Even with recent effort to replace major parts of the aircraft with composite, Al alloys continue to play a major role in the industry. Thus, the importance of Al alloys in vital components of aircraft has caused an unending research for improved Al alloys. L

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